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Commit c1e3b377 authored by Zhao Yakui's avatar Zhao Yakui Committed by Andi Kleen
Browse files

ACPI: Create "idle=halt" bootparam 



"idle=halt" limits the idle loop to using
the halt instruction.  No MWAIT, no IO accesses,
no C-states deeper than C1.

If something is broken in the idle code,
"idle=halt" is a less severe workaround
than "idle=poll" which disables all power savings.

Signed-off-by: default avatarZhao Yakui <yakui.zhao@intel.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
parent 5b53496a

Documentation/kernel-parameters.txt

+3 −1
Original line number Diff line number Diff line
@@ -818,7 +818,7 @@ and is between 256 and 4096 characters. It is defined in the file 
			See Documentation/ide/ide.txt.



	idle=		[X86]

			Format: idle=poll or idle=mwait

			Format: idle=poll or idle=mwait, idle=halt

			Poll forces a polling idle loop that can slightly improves the performance

			of waking up a idle CPU, but will use a lot of power and make the system

			run hot. Not recommended.
@@ -826,6 +826,8 @@ and is between 256 and 4096 characters. It is defined in the file 
			to not use it because it doesn't save as much power as a normal idle

			loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same

			as idle=poll.

			idle=halt. Halt is forced to be used for CPU idle.

			In such case C2/C3 won't be used again.



	ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem

			Claim all unknown PCI IDE storage controllers.

arch/ia64/kernel/process.c

+2 −0
Original line number Diff line number Diff line
@@ -55,6 +55,8 @@ void (*ia64_mark_idle)(int); 


unsigned long boot_option_idle_override = 0;

EXPORT_SYMBOL(boot_option_idle_override);

unsigned long idle_halt;

EXPORT_SYMBOL(idle_halt);



void

ia64_do_show_stack (struct unw_frame_info *info, void *arg)

arch/x86/kernel/process.c

+16 −1
Original line number Diff line number Diff line
@@ -7,6 +7,10 @@ 
#include <linux/module.h>

#include <linux/pm.h>

#include <linux/clockchips.h>

#include <asm/system.h>



unsigned long idle_halt;

EXPORT_SYMBOL(idle_halt);



struct kmem_cache *task_xstate_cachep;
@@ -325,7 +329,18 @@ static int __init idle_setup(char *str) 
		pm_idle = poll_idle;

	} else if (!strcmp(str, "mwait"))

		force_mwait = 1;

	else

	else if (!strcmp(str, "halt")) {

		/*

		 * When the boot option of idle=halt is added, halt is

		 * forced to be used for CPU idle. In such case CPU C2/C3

		 * won't be used again.

		 * To continue to load the CPU idle driver, don't touch

		 * the boot_option_idle_override.

		 */

		pm_idle = default_idle;

		idle_halt = 1;

		return 0;

	} else

		return -1;



	boot_option_idle_override = 1;

drivers/acpi/processor_idle.c

+22 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ 
#include <linux/pm_qos_params.h>

#include <linux/clockchips.h>

#include <linux/cpuidle.h>

#include <linux/cpuidle.h>



/*

 * Include the apic definitions for x86 to have the APIC timer related defines
@@ -57,6 +58,7 @@ 


#include <acpi/acpi_bus.h>

#include <acpi/processor.h>

#include <asm/processor.h>



#define ACPI_PROCESSOR_COMPONENT        0x01000000

#define ACPI_PROCESSOR_CLASS            "processor"
@@ -955,6 +957,17 @@ static int acpi_processor_get_power_info_cst(struct acpi_processor *pr) 
			} else {

				continue;

			}

			if (cx.type == ACPI_STATE_C1 && idle_halt) {

				/*

				 * In most cases the C1 space_id obtained from

				 * _CST object is FIXED_HARDWARE access mode.

				 * But when the option of idle=halt is added,

				 * the entry_method type should be changed from

				 * CSTATE_FFH to CSTATE_HALT.

				 */

				cx.entry_method = ACPI_CSTATE_HALT;

				snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");

			}

		} else {

			snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI IOPORT 0x%x",

				 cx.address);
@@ -1780,6 +1793,15 @@ int __cpuinit acpi_processor_power_init(struct acpi_processor *pr, 
		return 0;



	if (!first_run) {

		if (idle_halt) {

			/*

			 * When the boot option of "idle=halt" is added, halt

			 * is used for CPU IDLE.

			 * In such case C2/C3 is meaningless. So the max_cstate

			 * is set to one.

			 */

			max_cstate = 1;

		}

		dmi_check_system(processor_power_dmi_table);

		max_cstate = acpi_processor_cstate_check(max_cstate);

		if (max_cstate < ACPI_C_STATES_MAX)

include/asm-ia64/processor.h

+1 −0
Original line number Diff line number Diff line
@@ -763,6 +763,7 @@ prefetchw (const void *x) 
#define spin_lock_prefetch(x)	prefetchw(x)



extern unsigned long boot_option_idle_override;

extern unsigned long idle_halt;



#endif /* !__ASSEMBLY__ */